5o8 
The  Phenomena  of  Catalysis. 
(Am.  Jour.  Pharm. 
\  November,  1913. 
of  solution  is  also  not  a  criterion.  While  these  two  react  readily 
when  dissolved  in  water,,  they  need  not  react  appreciably  when  dis- 
solved in  some  other  solvent.  This  catalytic  action  of  water,  so 
common  as  to  be  usually  lost  sight  of  as  a  case  of  catalysis, 
is  a  very  marked  case  because  of  its  sensitiveness.  The  most 
refined  methods  have  had  to  be  employed  to  remove  the  water  in 
cases  where  its  effect  was  to  be  studied.  For  example,  the  ordinary 
explosion  of  carbon  monoxide  (CO)  with  oxygen  does  not  take 
place  if  the  gases  are  perfectly  dried,  but  a  trace  of  moisture  makes 
it  easy  to  start  the  reaction  by  a  spark.  Such  active  agents  as 
gaseous  hydrochloric  acid  and  ammonia,  which  combine  readily  at 
ordinary  temperatures,  do  not  react  in  entire  absence  of  water. 
And  the  decomposition  or  dissociation  of  ammonium  chloride  which 
in  any  ordinary  experiment  is  readily  brought  about  by  moderate 
heating,  will  not  occur  in  absence  of  traces  of  moisture. 
The  method  of  action  may  not  be  the  same  in  these  various 
cases,  but  the  resulting  great  increase  in  velocity  of  action  or  even 
apparent  production  of  the  possibility  of  reaction  and  the  non- 
consumption  of  the  foreign  matter  or  catalyst  is  common  to  them  all. 
There  are  many  other  such  reactions. 
The  various  types  of  catalysis  apparently  differ  widely,  and  while 
they  possess  in  common  the  peculiarity  which  coordinated  them 
under  this  head,  they  are  being  subdivided  and  grouped  under  new 
classifications  because  differentiating  characteristics  become  grad- 
ually better  understood.  For  example :  there  is  a  large  group  of 
chemical  processes  which  are  catalyzed  by  the  presence  of  solids ; 
sometimes  by  a  specific  solid,  such  as  platinum,  in  other  cases  by 
a  particular  state  or  property  of  a  solid,  such  as  fine  subdivision 
or  large  surface  area,  etc.  A  little  palladium  or  osmium  will  ignite 
illuminating  gas  at  the  burner-tip  in  air.  Some  platinum,  vanadium 
oxide,  or  even  iron  oxide  will  bring  about  the  rapid  union  of  sulphur 
dioxide  and  oxygen.  These  may  be  classed  as  surface  effects, 
as  absorption  effects,  etc.,  while  it  is  not  probable  that  reactions 
which  owe  their  procedure  to  liquid  or  gaseous  water  can  be  so 
classed. 
A  number  of  catalyses  may  be  looked  upon  as  being  due  to  the 
formation,  for  a  short  time,  of  products  containing  the  catalyzer 
and  one  or  both  of  the  reacting  substances,  the  catalyzer  later  step- 
ping out  of  the  reaction  at  its  completion,  much  as  the  marrying 
parson  leaves  the  wedding  ceremony  with  his  marrying  power  un- 
